2-vinyl-fluorenone and derivatives thereof

ABSTRACT

Disclosed is a composition of matter characterized by the structural formula: ##STR1## wherein R 1  is hydrogen or methyl and R 2 , R 3  and R 4  are hydrogen, halogen substituted or unsubstituted alkyl groups containing 1 to 4 carbon atoms. Also disclosed are vinyl polymers of the above compounds.

BACKGROUND OF THE INVENTION

Fluorenone and 2-vinylfluorene are known compounds. However, theoxidation of 2-vinylfluorene to 2-vinylfluorenone is problematical dueto the reaction of the vinyl group during oxidation. In order to convert2-vinylfluorene to 2-vinylfluorenone it is necessary to employ anoxidant which is sufficiently strong to cause the desired oxidationwithout causing prepolymerization or other undesirable side reactions.

Preparation of 2-vinylfluorenone would be desirable since it can bepolymerized to provide poly-2-vinylfluorenone. This polymer is ofinterest since it has been found to be an excellent insulator which canbe applied to conductive substrates from solution. The monomersthemselves possess this insulating property; however, it is preferred topolymerize the monomer before its application to the substrate or tocause polymerization in situ after such application due to the enhancedmechanical properties of the polymer film as compared to a film of themonomer. However, the inability of the prior art to come up with amethod to prepare 2-vinylfluorenone has hindered attempts to prepare thepolymer. An alternate route for preparation of the polymer, i.e.preparation of poly-2-vinylfluorene with subsequent oxidation of thefluorene units to fluorenone, has not been entirely successful. Forexample, it is reported in Polymer Letters, Vol. 9, pp. 671-676 (1971)that a 50/50 copolymer of 2-vinylfluorene/2-vinylfluorenone can beprepared by the oxidation of poly-2-vinylfluorene with chromium trioxidein glacial acetic acid. This reference illustrates the difficulty ofobtaining complete oxidation by pointing out that a residue having anoxygen analysis indicating almost complete conversion topoly-2-vinylfluorenone was insoluble in organic solvents and strongacids. This insolubility, which is probably due to extensivecrosslinking during the oxidation, is undesirable since the polymerscannot be applied to substrates from their solutions in organicsolvents. It appears, from the state of the art, that the only way toprepare poly-2-vinylfluorenone containing no fluorene units in a formwhich is soluble in common organic solvents is to prepare2-vinylfluorenone and cause its polymerization.

Accordingly, it would be desirable and it is an object of the presentinvention to provide a method for the preparation of 2-vinylfluorenone.

An additional object is to provide, as a composition of matter,2-vinylfluorenone, α-methyl-2-vinylfluorenone and substitutedderivatives thereof.

An additional object is to provide polymers of 2-vinylfluorenone,α-methyl-2-vinylfluorenone and substituted derivatives thereof.

A further object is to provide copolymers of 2-vinylfluorenone,α-methyl-2-vinylfluorenone and substituted derivatives thereof withother vinyl monomers.

SUMMARY OF THE INVENTION

The present invention is a composition of matter characterized by thestructural formula: ##STR2## In the above formula R₁ is hydrogen ormethyl and R₂, R₃ and R₄ are hydrogen, halogen, substituted orunsubstituted alkyl groups containing 1 to 4 carbon atoms or alkoxy inits stead.

The above-described composition is prepared by reacting a composition ofthe formula: ##STR3## wherein R₁, R₂, R₃ and R₄ are as defined abovewith benzyltrimethyl ammonium hydroxide and oxygen in a suitable solventto oxidize the fluorene to fluorenone.

DETAILED DESCRIPTION

The novel compounds of the present invention are characterized by theformula: ##STR4##

In the above formula, R₁ is H or methyl. The remaining constituents,i.e. R₂, R₃ and R₄ are either H, halogen, substituted or unsubstitutedalkyl groups containing 1 to 4 carbon atoms or alkoxy. Examples of R₂,R₃ and R₄ include alkyl or substituted alkyl, e.g. methyl, ethyl,chloroethyl, cyanoethyl, propyl, butyl, and isobutyl. In addition, theR₂, R₃ and R₄ substituents can be halogen; e.g. bromo, chloro or fluoro;or alkoxy; e.g. methoxy, ethoxy, propoxy or butoxy. In general, thecomposition in which the R substituents are H, i.e. 2-vinyl fluorenone,is preferred.

These compositions are prepared by the controlled oxidation of2-vinylfluorene. Great care must be taken in selecting an oxidant thatis neither too mild nor too strong. Too mild an oxidant will not convertthe fluorene to fluorenone, whereas too strong an oxidant will causepremature polymerization or oxidative reactions of the vinylsubstituent. It has been discovered that 2-vinylfluorenone can beprepared in good yields without appreciable polymerization by reacting,in a suitable solvent, 2-vinylfluorene with benzyltrimethyl ammoniumhydroxide and oxygen. This process can also be used to prepare thederivatives of 2-vinylfluorenone and α-methyl-2-vinylfluorenonedescribed above.

After preparation, the 2-vinylfluorenone or derivative thereof can bepolymerized either by bulk or solution polymerization or emulsiontechniques to provide poly-2-vinylfluorenone or derivatives thereofcharacterized by the formula: ##STR5## where R₁, R₂, R₃ and R₄ are asdefined above and n is a number representing the degree ofpolymerization.

This polymerization, which can be initiated either by free radical orcationic initiators, can also be used to provide copolymers of2-vinylfluorenone and other vinyl monomers. Examples of other vinylmonomers which may be copolymerized with 2-vinylfluorenone includestyrene, vinyl chloride, methyl methacrylate, vinyl carbazole, vinylnaphthalene, methyl acrylate, isoprene, butadiene, substituted styrenes,acrylonitrile and vinyl acetate.

The degree of polymerization which can be obtained will vary dependingon the polymerization technique. Generally, a degree of polymerizationof up to 1000 may readily be obtained and higher degrees ofpolymerization are possible. A degree of polymerization of from 10 to5000 is typical.

The invention is further illustrated by the following examples in whichall percentages are by weight unless otherwise specified.

EXAMPLE I

Synthesis of 2-vinylfluorene is carried out as follows:

Triphenylmethyl phosphonium bromide (36 gms/0.1 mole) in 500 millilitersof dry THF is treated under nitrogen with 90 milliliters of a 1.1 molarsolution of n-butyl lithium in hexane and stirred for 2 hours. Asolution of 19.4 gms. (0.1 mole) of fluorene-2-carboxaldehyde in 100milliliters of THF is added dropwise and the final mixture refluxed for11/2 hours. One liter of hexane is added to the cold solution and theprecipitate filtered off. The filtrate is evaporated and the residuechromatographed on alumina (Woehlm neutral) using hexane to give 15 gms.(75% theory) of product. Recrystallization from hexane yields2-vinylfluorene as colorless plates. The structure of the product isconfirmed by nuclear magnetic resonance and elemental analysis.

EXAMPLE II

Synthesis of 2-vinylfluorenone is accomplished as follows:

The 2-vinylfluorene prepared in Example I is dissolved in 800milliliters of pyridine and cooled to 0° C. One-half milliliter of a 40%solution of benzyltrimethyl ammonium hydroxide in pyridine is slowlyadded with air being bubbled through the reaction solution. Theinitially formed red coloration fades over a period of 1 to 2 hours andthe solution is poured into water and extracted with benzene to yield 9grams (90% theory) of a yellow solid. The residue is chromatographed onalumina (Woehlm basic) and eluted with benzene. Recrystallization fromhexane gives 2-vinylfluorenone as a pale yellow material (melting point69°-70° C). The structure of the product is confirmed by nuclearmagnetic resonance and elemental analysis.

EXAMPLE III

Synthesis of α-methyl-2-vinylfluorenone is accomplished by acetylationof fluorene as described in Organic Synthesis, Collective, Vol. 3, page23. Conversion to the vinyl derivative is achieved in a 70% yield usingthe procedure described in Example I. Recrystallization of the productfrom hexane gives α-methyl-2-vinylfluorene as tan crystals (m.p.155°-156° C). The product is oxidized to the corresponding fluorenonederivative by the procedure described in Example II. Recrystallizationof the product from hexane yields α-methyl-2-vinylfluorenone as paleyellow crystals (m.p. 76°-77° C). The structure of the product isverified by nuclear magnetic resonance and elemental analysis.

Polymerization of 2-vinylfluorenone is accomplished in followingExamples IV - VII.

EXAMPLE IV

Emulsion

In a 1 liter Morton flask is placed 200 milliliters of H₂ O togetherwith 3 gms. of sodium oleate. The solution is blanketed with nitrogenand heated to 80°-85° C. At this point, 13.4 gm. (.065 moles) of2-vinylfluorenone are added to the flask. Subsequently, three portionsof a solution of 0.01 gm. of K₂ S₂ O₈ in 10 milliliters of H₂ O areadded over a period of 1 hour. The resulting solution is allowed to stirfor 6 hours and coagulated with 50 milliliters of a saturated sodiumacetate solution. The resulting precipitate is filtered and dried toyield 11.5 gm. of a polymer having a molecular weight of approximately350,000.

EXAMPLE V

Cationic

In a beverage bottle are placed 5 gm. (.024 M) of 2-vinylfluorenone and75 milliliters of methylene chloride to form a solution which issaturated with nitrogen. The bottle is capped and chilled to -30° Cwhereupon 0.10 milliliter of a BF₃.Et₂ O solution is added as catalystand the mixture stirred for 3 hours. The mixture is then quenched withmethanol to yield 3 gm. of a polymer having a molecular weight ofapproximately 10,000.

EXAMPLE VI Solution

In a polymer tube are placed 0.5 gm. (.0024 M) 2-vinylfluorenone; 0.007gm. (4 × 10⁻ ⁵ M) of AIBN and 15 milliliters of toluene. The tube isdegassed, sealed and heated to 85° C for 24 hours. The reaction productis dissolved in THF and precipitated with methanol to yield 0.35 gm. ofa polymer having a molecular weight of approximately 50,000.

EXAMPLE VII

Bulk

In a 100 milliliter round bottomed flask are placed 11.1 gm. (.05 M)2-vinylfluorenone and .005 gm. (3 × 10⁻ ⁵ M) of AIBN. The contents areblanketed with nitrogen and heated to 70°-75° C for 2 hours. Thereaction product is dissolved in THF and precipitated in benzene toyield 8 gm. of a polymer having a molecular weight of approximately200,000.

EXAMPLE VIII

Cationic polymerization of α-methyl-2-vinylfluorenone.

In a 100 milliliter flask are placed 2 gm. of α-methyl-2-vinylfluorenoneand 50 milliliters of chlorobenzene. The contents of the flask areblanketed with nitrogen and cooled to -40° C at which point a smallamount of BF₃ gas is added. The reaction mass, which turned red upon theaddition of the BF₃, is kept below -30° C with stirring for 3 hours. Thereaction is quenched with methanol and precipitated with methanol toyield 0.5 gm. of a polymer having a molecular weight of approximately10,000.

EXAMPLE IX

A copolymer of 2-vinylfluorenone and N-vinylcarbazole is prepared asfollows:

In a polymer tube are placed 1.1 gm. (.005 M) of 2-vinylfluorenone; 0.95gm. (.005 M) of N-vinylcarbazole; 5 milliliters of benzene and 0.048 gm.(2 × 10⁻ ⁴ M) benzoyl peroxide. The tube is degassed, sealed and heatedto 65° C for 18 hours. The resulting product is precipitated intomethanol to give an eighty percent yield of a coploymer containingapproximately 80 mole % of 2-vinylfluorenone and 20 mole % ofN-vinylcarbazole.

The polymers of the instant invention possess excellent dielectric andinsulating properties making them ideal materials for use in thinpolymer film capacitors. Furthermore, the polymers exhibit good thermalstability at elevated temperatures up to 150° C. The polymers possessdielectric constants of approximately 4(100 Hz) over the temperaturerange of -200° to 50° C with a dielectric loss factor of less than 0.1at the same frequency.

The polymers can be used to fabricate capacitors using either solventcoating or in situ polymerization techniques.

EXAMPLE X

A solution of poly-2-vinylfluorenone is prepared by dissolving thepolymer in benzene. The solution is coated on a thin aluminum film usinga doctor blade technique and the solvent evaporated to provide a polymerfilm approximately 2.5 μ thick.

This metal/insulator sheet is cut into units of the desired dimensionstwo of which are positioned so as to allow contact leads to be attached,rolled into a compact cylinder and potted in an epoxy type resin toproduce a functioning capacitor.

EXAMPLE XI

A standard paper/aluminum foil capacitor is impregnated with a solutionof 2-vinylfluorenone and AIBN in benzene. The monomer is polymerizedusing heat as the stimulus and potted as previously described to providethe finished capacitor.

What is claimed is:
 1. A composition of matter characterized by thestructural formula: ##STR6## wherein R₁ is hydrogen or methyl and R₂, R₃and R₄ are hydrogen, halogen, substituted or unsubstituted alkyl groupscontaining 1 to 4 carbon atoms or alkoxy groups containing 1 to 4 carbonatoms.
 2. The composition of claim 1 wherein R₂, R₃ and R₄ are H.
 3. Thecomposition of claim 2 wherein R₁ is H.
 4. 2-vinylfluorenone.
 5. Amethod of preparing a composition of matter characterized by thestructural formula: ##STR7## wherein R₁ is H or methyl and R₂, R₃ and R₄are hydrogen, halogen, substituted or unsubstituted alkyl groupscontaining 1 to 4 carbon atoms or alkoxy groups containing 1 to 4 carbonatoms which comprises reacting, in a suitable solvent, a compositioncharacterized by the structural formula: ##STR8## wherein R₁, R₂, R₃ andR₄ are as defined above with benzyltrimethyl ammonium hydroxide/oxygento thereby oxidize the fluorene group to fluorenone.
 6. The method ofclaim 5 wherein R₂, R₃ and R₄ are H.
 7. The method of claim 6 wherein R₁is H.
 8. The method of claim 5 wherein the solvent is pyridine.